please, no more variables (even if you document them). if you want to enable epel_testing somewhere, just do
```
variable OS_REPOSITORY_LIST ?= {append('epel_testing')};
```
instead of 
```
final REPOSITORY_EPEL_TESTING_ENABLED = true;
```
and yes, just call your repo epel_testing. the name should be OS independent. the url of the repo can be made OS aware, that's the only thing that matters. (i can check for some example code if you like)